(a) Field of the Invention
The present invention relates to an automatic transmission for a vehicle, more particularly, to a planetary gear train of the automatic transmission capable of realizing at least ten forward speeds, thereby improving power delivery performance and fuel consumption due to multi-stages, and improving driving stability by utilizing a low rotation speed of an engine.
(b) Description of the Related Art
Generally, in automatic transmissions, achieving more shift stages can maximize fuel consumption and driving efficiency.
In particular, engine research has been undertaken to achieve weight reduction and to enhance fuel consumption by so-called downsizing, and research on an automatic transmission has been performed to simultaneously provide better drivability and fuel consumption by achieving more shift stages.
In order to achieve more shift stages for an automatic transmission, the number of parts, particularly the number of planetary gear sets is typically increased and installability, production cost, weight, and/or power flow efficiency according to total length of transmission may be increased.
Therefore, in order to maximize fuel consumption of an automatic transmission having more shift stages, it is important for better efficiency to be derived by a smaller number of parts.
In this respect, an eight-speed automatic transmission has been recently introduced, and a planetary gear train for an automatic transmission enabling more shift stages is continuously required.
However, the majority of general automatic transmissions having more than eight speeds include three to four planetary gear sets and five to six control elements (friction elements), in this case, total length is increased, which has drawbacks of deteriorating installability.
As a result, plural rows structures of planetary gear sets have been adopted, or a dog clutch is applied in place of wet control elements. However, in this case, applicable structure is restricted and shift feel is deteriorated by applying the dog clutch.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.